The twin brother of Poland's president has been chosen by the governing Law and Justice party to take over as head of government, after the prime minister formally submits his resignation on Monday. The political infighting could make Poland the only country with identical twins as president and prime minister.

Przemyslaw Gosiewski, head of Poland's Law and Justice parliamentary group announced the party's choice to succeed Prime Minister Kazimierz Marcinkiewicz.

He said party leader Jaroslaw Kaczynski was chosen to succeed Marcinkiewicz, who did not say why he was resigning. There have been reports in recent weeks of differences between Marcinkiewicz and the Kaczynskis over economic policies and taking government decisions without consulting coalition partners.

Jacek Kucharczyk, the head of Poland's Public Affairs Institute, says the prime minister became a victim of his popularity with Polish voters. "I think we can safely assume that Prime Minister Marcinkiewicz has become too independent," he said. "Prime Minister Marcinkiewicz has been trying to build up his own political position, using his very high popularity. And, I think that he made the assumption that the party's leadership would not get rid of such a popular politician, and took some risk. I think that he simply over calculated."

The Law and Justice party sought to limit the damage on Saturday by asking him to run as its candidate for the post of Warsaw mayor.

If Jaroslaw Kaczynski is confirmed as the new prime minister by parliament next week, Poland will become the only country with identical twins as head of state and government. His twin brother, Lech Kaczynski, was elected president in October, following his unexpected victory over a liberal, pro-business candidate.

Jaroslaw Kaczynski admitted to reporters there was a certain risk for the president and prime minister to be brothers, but stressed his conservative Law and Justice Party concluded a different candidate would be a worse way out.

Critics view the Kaczynskis, former anti-communist activists, with skepticism because of their awkward ruling alliance with fringe nationalists and leftists, and their perceived anti-European Union feelings.

Economist Witold Orlowski, of Price Waterhouse Cooper, says there is concern among international investors that Jaroslaw Kaczynski is a eurosceptic, suspicious of foreign business. "He seems to be not very much interested in economic issues. That's kind of a challenge, because the new prime minister must make quite rapid announcements to clarify his views. This is the only way to make business feel secure about the economic policies of the Polish government," he said.

Poland is the largest economy among the 10 newest European Union members.